I only have 'Let Mortal Heroes Sing Your Fame', but I will definitely be getting more.
It's strange that it wasn't really what I was expecting, but yet just as good if not better than my expectations (which were already high due to the praise they get).
On the said album, there's hardly a conventional metal technique to be found, and yet it is still thoroughly "metal" in spirit. I think Guardian of Darkness summed up their music well on metal archives when he was talking about them as the victorious warriors after the war. Looking at them this way helps to place them logically after the standard black metal sound, but still fits them in with it.
The music itself is mesmerising, hypnotic and beautiful, and frankly I enjoy it a lot more than many other acclaimed BM releases, not least for its refreshing aproach lyrically and conceptually.
You wont be disappointed.